xref: /linux/drivers/tty/Kconfig (revision bdcffc5a1a28b566a38a4b0d5bcefc78a97f4ecb)

config VT
	bool "Virtual terminal" if EXPERT
	depends on !S390
	select INPUT
	default y
	---help---
	  If you say Y here, you will get support for terminal devices with
	  display and keyboard devices. These are called "virtual" because you
	  can run several virtual terminals (also called virtual consoles) on
	  one physical terminal. This is rather useful, for example one
	  virtual terminal can collect system messages and warnings, another
	  one can be used for a text-mode user session, and a third could run
	  an X session, all in parallel. Switching between virtual terminals
	  is done with certain key combinations, usually Alt-<function key>.

	  The setterm command ("man setterm") can be used to change the
	  properties (such as colors or beeping) of a virtual terminal. The
	  man page console_codes(4) ("man console_codes") contains the special
	  character sequences that can be used to change those properties
	  directly. The fonts used on virtual terminals can be changed with
	  the setfont ("man setfont") command and the key bindings are defined
	  with the loadkeys ("man loadkeys") command.

	  You need at least one virtual terminal device in order to make use
	  of your keyboard and monitor. Therefore, only people configuring an
	  embedded system would want to say N here in order to save some
	  memory; the only way to log into such a system is then via a serial
	  or network connection.

	  If unsure, say Y, or else you won't be able to do much with your new
	  shiny Linux system :-)

config CONSOLE_TRANSLATIONS
	depends on VT
	default y
	bool "Enable character translations in console" if EXPERT
	---help---
	  This enables support for font mapping and Unicode translation
	  on virtual consoles.

config VT_CONSOLE
	bool "Support for console on virtual terminal" if EXPERT
	depends on VT
	default y
	---help---
	  The system console is the device which receives all kernel messages
	  and warnings and which allows logins in single user mode. If you
	  answer Y here, a virtual terminal (the device used to interact with
	  a physical terminal) can be used as system console. This is the most
	  common mode of operations, so you should say Y here unless you want
	  the kernel messages be output only to a serial port (in which case
	  you should say Y to "Console on serial port", below).

	  If you do say Y here, by default the currently visible virtual
	  terminal (/dev/tty0) will be used as system console. You can change
	  that with a kernel command line option such as "console=tty3" which
	  would use the third virtual terminal as system console. (Try "man
	  bootparam" or see the documentation of your boot loader (lilo or
	  loadlin) about how to pass options to the kernel at boot time.)

	  If unsure, say Y.

config HW_CONSOLE
	bool
	depends on VT && !S390 && !UML
	default y

config VT_HW_CONSOLE_BINDING
       bool "Support for binding and unbinding console drivers"
       depends on HW_CONSOLE
       default n
       ---help---
         The virtual terminal is the device that interacts with the physical
         terminal through console drivers. On these systems, at least one
         console driver is loaded. In other configurations, additional console
         drivers may be enabled, such as the framebuffer console. If more than
         1 console driver is enabled, setting this to 'y' will allow you to
         select the console driver that will serve as the backend for the
         virtual terminals.

	 See <file:Documentation/console/console.txt> for more
	 information. For framebuffer console users, please refer to
	 <file:Documentation/fb/fbcon.txt>.

config UNIX98_PTYS
	bool "Unix98 PTY support" if EXPERT
	default y
	---help---
	  A pseudo terminal (PTY) is a software device consisting of two
	  halves: a master and a slave. The slave device behaves identical to
	  a physical terminal; the master device is used by a process to
	  read data from and write data to the slave, thereby emulating a
	  terminal. Typical programs for the master side are telnet servers
	  and xterms.

	  Linux has traditionally used the BSD-like names /dev/ptyxx for
	  masters and /dev/ttyxx for slaves of pseudo terminals. This scheme
	  has a number of problems. The GNU C library glibc 2.1 and later,
	  however, supports the Unix98 naming standard: in order to acquire a
	  pseudo terminal, a process opens /dev/ptmx; the number of the pseudo
	  terminal is then made available to the process and the pseudo
	  terminal slave can be accessed as /dev/pts/<number>. What was
	  traditionally /dev/ttyp2 will then be /dev/pts/2, for example.

	  All modern Linux systems use the Unix98 ptys.  Say Y unless
	  you're on an embedded system and want to conserve memory.

config DEVPTS_MULTIPLE_INSTANCES
	bool "Support multiple instances of devpts"
	depends on UNIX98_PTYS
	default n
	---help---
	  Enable support for multiple instances of devpts filesystem.
	  If you want to have isolated PTY namespaces (eg: in containers),
	  say Y here.  Otherwise, say N. If enabled, each mount of devpts
	  filesystem with the '-o newinstance' option will create an
	  independent PTY namespace.

config LEGACY_PTYS
	bool "Legacy (BSD) PTY support"
	default y
	---help---
	  A pseudo terminal (PTY) is a software device consisting of two
	  halves: a master and a slave. The slave device behaves identical to
	  a physical terminal; the master device is used by a process to
	  read data from and write data to the slave, thereby emulating a
	  terminal. Typical programs for the master side are telnet servers
	  and xterms.

	  Linux has traditionally used the BSD-like names /dev/ptyxx
	  for masters and /dev/ttyxx for slaves of pseudo
	  terminals. This scheme has a number of problems, including
	  security.  This option enables these legacy devices; on most
	  systems, it is safe to say N.


config LEGACY_PTY_COUNT
	int "Maximum number of legacy PTY in use"
	depends on LEGACY_PTYS
	range 0 256
	default "256"
	---help---
	  The maximum number of legacy PTYs that can be used at any one time.
	  The default is 256, and should be more than enough.  Embedded
	  systems may want to reduce this to save memory.

	  When not in use, each legacy PTY occupies 12 bytes on 32-bit
	  architectures and 24 bytes on 64-bit architectures.